Grade 3 › G3U12 Time: Telling Time

Grade 3 › G3U12 Time: Telling Time › L4
GRADE 3 · ALBERTAOUTCOME AB-G3-3T1

L4 · Time of day in one 24-hour cycle

Learning goal

“I can express a time of day in one 24-hour cycle: hours count 0 to 23 from midnight, so afternoon and evening times add 12 to the hour - and I can change a 24-hour time back to a.m./p.m.”

24-hour cycle — counting the hours of one whole day from 0 to 23, starting at midnight, with no a.m. or p.m. needed.
Midnight — the middle of the night, where one day ends and the next begins. In the 24-hour cycle it is hour 0.
Noon — the middle of the day. In the 24-hour cycle it is 12:00, the same number as on a 12-hour clock.
Worked example

Lay out one whole day as a line of hours. Step 1: The day starts at midnight. In the 24-hour cycle, midnight is hour 0, so the middle of the night is written like 0:30 or 2:00. Step 2: The morning hours keep their clock numbers: 7:00 a.m. is 7:00, and 11:00 a.m. is 11:00. Noon is 12:00 - the same in both systems. Step 3: After noon the count keeps going instead of starting over: 1:00 p.m. is 13:00, 6:00 p.m. is 18:00, and the day's last hour starts at 23:00 (11:00 p.m.). Then midnight comes and the new day starts again at 0. Say it plainly: the 24-hour cycle never repeats an hour, so it never needs a.m. or p.m. Every time of day has exactly ONE name in the cycle.

Check yourself — explain it

Why does the 24-hour cycle not need a.m. and p.m.?

Paired problem — example still visible

Write 5:00 p.m. in the 24-hour cycle. -> 17:00 (5 + 12 = 17)

Faded completion — last step is yours

"8:00 p.m. = 8 + 12 = ___:00 in the 24-hour cycle." -> 20

Ready to practise?

10 scored questions with a 3-rung hint ladder. Mastery needs 8/10 plus both gate questions.

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